Some personal computers or special computers such as large industrial computers do not have a start/stop button or have the start/stop switch located at a position difficult to access by users. Hence providing an automatic start function is required. Take the personal computer as an example. The motherboard adopted ATX (Advanced Technology eXtended) specification is widely used that has a power supply including at least one main power system and one standby power system. The main power system mainly aims to transform AC of an external power source to DC in an ON condition to supply the motherboard. The standby power provides standby power to maintain continuous operation of the motherboard whether in the ON or OFF condition as long as the power supply is electrically connected. It usually is +5V. Namely while the power supply is connected to the external power source, the motherboard has a small loading current to provide basic power required to start the computer. In general, as the motherboard always has this loading current the computer can be started by depressing a pushbutton like a conventional power supply. Moreover, it also can be started through a network, peripheral devices (such as mouse, keyboard) or a timer. All these start operations require a trigger action from users. This has to be done through a medium to provide an active start signal to activate the computer.
Although most motherboards at present provide automatic start function, namely a direct start takes place after being connected to electric power. However, power supply system management still has to be set in advance in the Basic Input/Output System (BIOS) so that the host can be driven and started after the power supply system of the computer is electrically energized. Such an automatic start method relies on a battery power on the motherboard rather than the standby power. Hence trying to do automatic start by setting the BIOS could fail due to insufficient battery power of the motherboard.